The Health Plan Employer Data and Information Set (HEDIS) is a program from NCQA in the United States that consists of several measures by which the performance of a health plan can be compared to other plans, national or regional benchmarks, or the plan's performance from previous years. HEDIS is part of NCQA's accreditation process, although many plans choose to gather and submit HEDIS data without seeking accreditation. A strong motivation for many health plans to collect HEDIS data is that CMS requires HMOs to submit Medicare HEDIS data in order to be eligible to provide HMO services for Medicare enrollees under a program called Medicare Advantage. HEDIS was first released in 1993 as HEDIS 2.0. The latest version, HEDIS 2006, reports in general on 2005 data and comprises 67 measures.

HEDIS measures are divided into eight domains: Effectiveness of Care, Access/Availability of Care, Satisfaction With the Experience of Care, Health Plan Stability, Use of Services, Cost of Care, Informed Health Care Choices, and Health Plan Descriptive Information. Two domains, Cost of Care and Informed Health Care Choices, do not currently contain any measures, however. Measures are added, deleted, and revised annually in an attempt to capture relevant information. For example, a measure that dealt with the length of stay for women after giving birth was removed after it was determined that legislation mandating a certain minimum length of stay had rendered this measure nearly useless. Increased attention to medical care for seniors in recent years prompted the addition of a measure related to glaucoma screening for older adults. Other health care concerns covered by HEDIS are immunizations, cancer screenings, treatment after heart attacks, diabetes, asthma, flu shots, access to services, dental care, alcohol and drug dependence treatment, timeliness of handling claims and phone calls, prenatal and postpartum care, mental health care, well-care or preventive visits, inpatient utilization, drug utilization, and distribution of members by age, sex, and product lines.

HEDIS data are collected mostly through administering surveys, reviewing submitted insurance claims, and reviewing medical charts. Some measures offer a choice of how to collect data. For example, in the Effectiveness of Care measure titled Childhood Immunization Status, health plans identify children meeting certain enrollment and age criteria, then report what percentage of these children have received certain immunizations. Plans may collect data for this measure by reviewing insurance claims (referred to as the administrative method), but this method will not report children receiving immunizations at free clinics or other settings that do not submit insurance claims. For this measure, plans are allowed to supplement data collected from claims by reviewing medical charts and other immunization records (referred to as the hybrid method). By doing so, plans may identify many more immunizations and be able to report much more favorate rates, but this process is more costly, more time-consuming, and requires cooperation with nurses or other medical professionals who are authorized to handle medical records. Recognizing the added burden that reviewing medical charts places on a plan, NCQA allows plans to select a random sample of members and then pull claims for those members only to determine the percentage to report.